When building the hot side, do people normally butt weld the pipes or measure twice, take to a muffler shop, have the 1 end expanded and slip joint weld? Looking at people's pictures it looks like butt weld and grind for pipe to pipe?

How about for flanges, normally butt welded or sized to slip into the flange and welded on the underside?

 

Butt welds are preferable to slip fits that are welded. Just make sure you clean up the insides of the pipes to smooth the transitions as much as possible.

 

butt welds are one of the weakest joint fit-ups possible-... but it is INDEFINATELY strong enough for what you are doing. just make sure you get full penetration and i'd personally not grind the weld as it is stronger that way.



slip-fit will be stronger but then again it doesn't need to be THAT strong. it MAY even improve the flow due to the amount of burn-through you may get w/ a butt weld.



flanges are not considered butt welds they are fillet welds either way will be strong enough. slip through may be easier for fabing purposes.



i hope this helped.